This invention relates to implosion resistant cathode ray tube envelopes and more particularly to a cathode ray tube envelope having a sealed face plate member and funnel member with a U-shaped pair of flat rimbands compressed against the face plate member by a tensioned strap member.
The prior art suggests numerous techniques for enhancing the resistance to fracture of a cathode ray tube envelope. One technique provides a one-piece rim member which is placed in surrounding relationship to the skirt portion of a face plate sealed to a funnel of a cathode ray tube envelope. A foam or resin tape is either intermediate the rim member and skirt portion or the space therebetween is filled with a back-filling resin whereupon heat is applied to effect a tensioned fit of the rim band about the face plate.
Another known technique for fabricating implosion resistant cathode ray tube envelopes is the so-called method of controlled devacuation. Therein, a pair of rimbands are shaped to the contour of a face plate member and compressed by a surrounding tension band. Normally, the rimbands extend over and cover a portion of the front edge of the face plate of the cathode ray tube.
Although the above-mentioned techniques have been and still are employed in numerous fabricated cathode ray tube envelopes, it has been found that the known rimband structures leave something to be desired. More specifically, it has been found that rimbands contoured to the face of the plate are relatively expensive, as compared with a flat ribbon-like material, and require more sophisticated and expensive handling apparatus. Moreover, the contours of the rimband are not particularly suitable for the numerous different size envelopes and have a tendency to undesirably distort upon application of a compressive force thereto.